Vehicle audio systems often have at least two pairs of speakers for stereo audio. In a car, one pair of speakers may typically be located in the front of the vehicle and another set of speakers may be located in the rear of the vehicle, typically mounted in a rear door or back shelf. The audio system may process an audio signal for the front set of speakers primarily for listening by the driver and passenger(s) sitting at the front of the vehicle. The audio system may separately process an audio signal for the rear set of speakers primarily for the passenger(s) sitting at the rear of the vehicle.